Preliminary observations regarding the use of iodine-125 in the management of choroidal melanoma.

When compared with Cobalt-60, the physical properties of Iodine-125 make it an attractive alternative therapy for consideration in the management of selected choroidal melanomas. The low-energy gamma emission can be nearly completely shielded by a thin sheet of gold 0.4 mm thick. Iodine-125 contained in a gold-backed episcleral plaque may reduce radiation exposure to non-target tissues of the eye including the optic nerve and macula. Iodine-125 is readily available, is adaptable to specific tumour locations and size, and offers very little radiation hazard to handlers. The physical characteristics of Iodine-125 are suitable for treatment of relatively large ocular tumours. Preliminary experience at the Mayo Clinic with Iodine-125 in the management of 12 patients with malignant melanoma to the choroid who have been followed between six months and two and a quarter years, indicate the effectiveness of Iodine-125 in promoting tumour shrinkage. In 11 of the 12 treated eyes, there is evidence of decreased tumour thickness as judged by ultrasonography and photography.